Rotary magnetic multiple switch



April 3, 1956 G. c. WALSH ROTARY MAGNETIC MULTIPLE SWITCH 5 Sheets-Sheet1 Filed Oct. 8, 1954 III I III II :HIHIII an m' FIGIEL FlGIE INVENTOR.

GEORGE C. WALSH AGENT April 3, 1956 Filed Oct. 8, 1954 G. C. WALSHSheets-Sheet 2 S 3 oTL LEvEL 0m LEvEL 43 44 E Z 45 i a. 26 40 lo- 2 6 PI 4 31 40 I 42 41 E g 49 24 42 49/ 5E 48 4s 48 g5 52 4e 30 5 E L E 5| \516 61% b, y 27 28 f E [4' 2 Z I7 55 FIG 11 INVENTOR.

GEORGE C. WALSH aaqiim H, dawn,

AGENT April 3, 1956 G. c. WALSH ROTARY MAGNETIC MULTIPLE SWITCH 5Sheets-Sheet Filed Oct. 8, 1954 Illllllllllll FIGI INVENTOR.

GEORGE C. WALSH AGENT April 3, 1956 c, WALSH 2,740,860

ROTARY MAGNETIC MULTIPLE SWITCH Filed 001.. 8, 1954 5 Sheets-Sheet 4(muaanaQb INVENTOR. GEORGE C. WALSH A ril 3, 1956 G. C. WALSH ROTARYMAGNETIC MULTIPLE SWITCH Filed Oct. 8, 1954 MAGNET APPLIED TO CLOSE IESINGLY IN SUOCESSION (G-CLOSED) HI H2 o MEASURING INSTRUMENT 5Sheets-Sheet 5 FIG. 1X1]:

(A- CLOSED) INVENTOR. GEORGE C. WALSH JZUZ CQ AGENT United tates PatentROTARY MAGNETIC MULTIPLE SWITCH George C. Walsh, Foxboro, Mass, assignorto The Foxboro Company, Foxboro, Mass, a corporation of MassachusettsApplication October 8, 1954, Serial No. 461,147

1 Claim. (Cl. 2130-87) This invention relates to electrical switches andhas particular reference to multiple switch units which use rotarymagnets to separately operate the several portions of the switch units.

A mechanically operated prior art multiple switch unit is disclosed inthe Cobbett Patent 2,184,611, issued December 26, 1939. This prior artstructure is operated by a rotary cam member and is used for connectingin serial manner a plurality of electrical circuits to a common circuit.

The present invention provides a generally improved rotary magnetmultiple switch which is specifically an improvement with respect to theCobbett switch mentioned above. The switch of the present invention,like that of the Cobbett patent above, is provided for connecting inserial manner a plurality of electrical circuits to a common circuit. Asan illustrative example of its use, the switch of this invention is acompact, efficient unit, designed for use with multi-record recorders,such as that disclosed in the Bowditch Patent 2,674,513, issued April 6,1954. The switch of the present invention may also be used, for example,as an improved stepping switch for segmental recording, or for scanningdevices.

The structure of the present invention is operable with a minimum offriction between the electrical contacts of the switch, with nomechanical operating connection between the switches and the switchoperating magnet and consequently with a minimum of torque. The switchesmay be provided normally closed, or as detailed herein, normally open.As a further feature the switch contacts of the unit of this inventionmay be operated in a bath of electrically non-conductive oil or in animmediate atmosphere of inert gas. These arrangements lengthen the lifeof the switch contacts and provide a safety factor when the switch isused in explosive or dirty atmospheres. With these arrangements there isno danger of igniting such atmospheres by arcing at the contactsincident to the making and breaking of the circuits embodying thecontacts. Further, the oil bath especially prevents contact oxidationand acts as a contact lubricant.

It is therefore an object of this invention to provide a new andimproved rotary magnetic multiple switch.

Other objects and advantages of this invention will be in part apparentand in part pointed out hereinafter, and in the accompanying drawings,wherein:

Figure I is an elevation of a switch unit embodying this invention;

Figlre II is a bottom view of the structure of Figure 1;

Figure III is a top view of the structure of Figure I;

Figure 1V is a view of the structure of Figure l in vertical centralsection, showing, for the sake of clarity, only two of the switches;

Figure V is an elevation of the switch mounting inner housing asstripped and removed from the structure of Figure I;

Figure V1 is a vertical central section of the structure of Figure V;

2,740,860 Patented Apr. 3, 1956 ice Figure VII is a perspective view ofthe magnet unit and gear as removed from the structure of Figure I;

Figure VIII is an exploded view, in perspective, of the magnet unit andgear of Figure VII;

Figure IX is a perspective view of a double switch structure for use inan embodiment of this invention;

Figure X is an exploded view, in perspective, of the double switch ofthe structure of Figure IX;

Figure XI is a switch circuit according to the present invention andembodying the double switch structures according to Figures IX and X;and

Figure XII is a switch circuit according to the present invention andembodying single switch structures as shown in Figure IV.

With reference to Figures I-III, the switch unit according to theillustrated embodiment of this invention is a generally cylindrical body10 which is provided with a support base 11, raised on a pair ofdiametrically opposite feet 12, with openings 13 therethrough to receivemounting bolts (not shown) as a means of securing the switch unit to asuitable support (also not shown). The main body of the support base 11is a base plate 14 generally in the shape of a star with four 90 degreespaced blunt legs 14'. The feet 12 are extensions of the outer ends oftwo opposite legs 14', and four uprights 15 extend up from the baseplate 14, one at the outer end of each of the legs 14'. Thus the supportbase 11 stands the switch body 10 away from its mounting (not shown) andprovides a protected opening 16 above the base plate 14 and below theswitch body it). A gear 17 is located in the opening 16 with a pinion 18meshed therewith and a pinion shaft 19 is provided for driving thepinion 18 which in turn drives the gear 17. As will be detailedhereinafter, rotation of the gear 17 results in rotation of a magnetunit as illustrated in Figure VII. This magnet unit is secured, as inFigures 1, II, and IV, to the base plate 14 by means of a threaded shaft20, extending through the center of the base plate 14 concentricallywith the longitudinal axis of the whole unit and secured by a nut 21 onthe under side of the base plate 14. The base plate uprights 15 supporta lower flange 22 of an inner housing 23 (Figure V). An outer,cylindrical housing 24 is mounted on the flange 22, and switchconnection wires 25 extend upward through the top of the switch unit, insealed and insulated relation therewith.

Figure TV shows the inner structure of the unit of Figure I. In thisshowing, for the sake of clarity, only two single switches 26 are showninstead of the six that may, for example, be used. In many instances,also, it is desirable to use double switches such as are illustrated inFigures IX and X, and, for example, six of such double switches may beused.

Thus Figure IV shows the support base 14, the inner housing 23, theswitches 26, the outer housing 24, and a magnet assembly 27.

Referring to Figures lV-Vi, the inner housing 23 comprises a centralcylindrical inverted cup 23, with the lower end thereof provided withthe flange 22 extending radially outward therefrom and having adownwardly facing nular channel 29 therein for receiving the base plateuprights 15, and an upwardly facing annular channel 30 for receiving andsealing the bottom edge of the outer housing 24. The inner housing 23has a transverse dividing wall 31 located about midway verticallythereof, as the bottom of inverted cup 23. A second and uprightcylindrical cup member 32, with a somewhat greater diameter than that ofthe inverted cup 28, is mounted on and sealed to the top of the dividingwall 31 in continuance of the structure of the'inner housing 23. Theside wall of the second cup member 32 is shown as cut out to form acircular series of equally spaced switch supports 33 which haverelatively wide portions for mounting the switches,

aradseo and relatively narrow portions for providing sufficient space toallow the switch connection wires to be taken into the second cup 32,from whence they are passed through a top plate 34 of the inner housing23. The top plate 34 is secured to the tops of all the switch supports33, and extends radially outward therefrom to terminate in an upwardlyextending annular flange 35 on which the top of the outer housing 24 ismounted and sealed by means of a downwardly facing annular channel 36(Figure lV), formed by the inturned top edge of the outer housing 24.

As shown in Figure IV, the assembly of the inner and outer housings 32and 24 provides a closed and sealed chamber 37 which is cylindrical atone end and cylindrically annular at the other (lower) end. in oneembodiment of this invention, this sealed chamber may be substantiallyfilled with a body of suitable electrically non-conductive oil as ameans of preventing switch contact arcing, with the result that switchesimmersed in the oil may be safely used in explosive atmospheres and thatthe switch contacts are longer lived.

The switch assemblies 26 (Figure IV) are mounted on the inner housinguprights 33. Only two switch assemblies and their supporting uprights333 are shown in Figure IV but the particular structure shown isdesigned to mount a total of six switch assemblies, in a circle withinthe closed chamber 37. Each switch assembly includes three flexible arms4! ill, and 42, with electrical insulation spacers 43 therebetween and ametal mounting bar 44 capping the assembly, and with the whole deviceheld together and secured to its upright 33 by a pair of screws 4-5. Theflexible arms to, 4-1, and .12 are in overlying alignment with eachother, all extending downward in the sealed chamber 3'7 and parallelwith the central, longitudinal axis of the entire switch unit. Flexiblearm 40 lies close to the inner wall of the sealed chamber annulus, witha magnetic material strip 46 secured thereto to lie between the flexiblearm 4d and the inner wall of the sealed chamber annulus.

As will be seen hereinafter, each magnetic strip 46 bears a purposefuland predetermined dimensional relation to the magnet assembly 27. Theflexible arm as, further, is provided with a laterally and outwardlyextending pin 417 for engaging the lower end portion of the flexible arm42. In the open condition of the switches 26, as shown at the right inFigure IV, the normal, at rest position of the flexible arm ill is at anangle laterally and radially away from the inner wall of the sealedchamber annulus. The result of this arrangement is that the flexible arm42 is held laterally outward with respect to the normal at rest positionof the arm 42.

Consequently, when the magnet assembly 27 is applied, by rotation, to aswitch in the condition shown at the right in Figure TV, the flexiblearm 4 19 is drawn toward the longitudinal axis of the whole switch unit,away from its normal at rest position, and the flexible arm 42 is thusallowed to move, also toward the longitudinal axis of the switch unitand toward its at rest position. As a result, the middle flexible arm iland the outer flexible arm 42 are engaged, through cooperatingelectrical contacts 43 and d9 thereon. The middle flexible arm ll isshorter than the other arms (4% and 42) so that the pin &7 from theflexible arm 4 d extends past the end of the middle flexible arm 411i toengage the outer flexible arm 42. The flexible arms 41 and 42 are partof the electrical path in the switch and they are provided withelectrical leads 4 and 42' to their respective switch connection wires(25). The flexible arm 4% is not part of the electrical circuit throughthe switch, but is simply the magnetic material carrier which biases theswitch to open con dition in the absence of a magnetic field as appliedto the magnetic strip 46 by the magnet in the magnet assembly 27.

The Figure IV left hand switch assembly 26 shows the positions of theflexible arms 40, 4-1, and 42, when the magnetic field has been appliedto that switch with the result that the switch contacts 4%; and 49 areengaged and the switch is closed. it may be noted here that the switchcontacts 48 and 49 are immersed in the body of electricallynonconductive oil.

The magnet assembly 27 is detailed in Figures IV, VII, and VIII. It ismounted on the shaft 20, the upper headed end 26 of which is fixed tothe inner housing (23) transverse wall structure formed by the sealedjuncture of the wall and the base of the upper cup member 32. A hearingsleeve 50 is mounted on the shaft 26 and is held between the under sideof the shaft head 20 and the base plate lid by the nut 21 on the lowerend of the shaft 20. Thus the shaft Zil is fixed, and the magnetassembly is mounted on the bearing sleeve St for rotation about theshaft Zil.

The magnet bearing sleeve 50, near its lower end, is provided with anannular outstanding shoulder 51. The magnet proper consists of a bottompole piece 52, the main body 53 of the magnet, and a top pole piece 54.The pole pieces 52 and 5d are in flat tear drop form, mounted on andextending transversely of the bearing sleeve 54 and each having a teardrop base opening through which the bearing sleeve 50 extends. The polepieces are arranged in overlying alignment with each other, and theapexes of the tear drop forms extend to adjacency (Figure IV) with theouter face of inner wall of the sealed chamber 3'7, and therefore intoadjacency with the magnetic strips 46 on the switches 26 within thesealed chamber.

The magnet main body 53 is in the form of a magnet which is sleevemounted on the bearing sleeve 54 between the pole pieces 52 and 54. Thedrive gear 17 is also mounted on the bearing sleeve, so as to abut onthe under side of the bearing sleeve shoulder 51. The bottom pole piecerests on the top side of the bearing sleeve shoulder Sit, and theassembly is held together by a pair of screws 55. The magnet sleeve isvertically slotted at one side to accommodate one of the screws 55. Themagnet body 53, the pole pieces 52 and 5d and the magnetic materialstrips 46 are the only members in the effective area of the magnet whichare susceptible to magnetic attraction. As shown in Figure IV, thedistance between the pole pieces 52 and 54 is approximated by the lengthof the magnetic material strips d'll on each of the switch assemblies26. The strips 40 thus extend essentially from pole to pole in themagnet and are sufiiciently close thereto to form an efficient fiuxguide for the magnetic field of the magnet. As a result, an efficientswitch unit is provided, with a relatively strong magnetic attractionthus provided for the operation of each of the switches.

Figures IX and X show a double switch unit which may be used instead ofthe single switch unit shown in Figure IV. With this arrangement, therotary magnet operates two switches at each rotary position, thusproviding, for example, a set of twelve switches operable in pairs.Figure X1 is a circuit showing of a set of double switches whereinsimultaneous breaks are made in two leads from each of a set oftemperature measuring electrical resistance elements G-L. in the showingof Figure XI, the rotary magnet is considered as applied to the doubleswitch G alone so that the switch contact pairs G1 and G2 are bothengaged, while the contact pairs of the other double switches H-L areall separated.

Figure XII is a circuit showing of a set of single switches AF likethose shown in Figure iV, wherein one lead of each of a set ofthermocouple elements AF' may be broken, respectively, by the contactsA-F. In this drawing, the rotary magnet is considered as applied to thesingle switch A alone so that the switch contact pair thereof isengaged, while the contact pairs of the other Single switches B-F areall separated.

The circuit showings of Figures X1 and XEI are in tended to be merelyillustrative of possible wiring connections of rotary magnet switchesembodying this invention, for example, as applied to switch structurelike that illustrated in Figure IV.

Again referring to Figures iX and X, the double switch assemblycomprises two sets of fiexures 56, 57, and 53, 59, comparable to theflexure set 41, 42 of Figure IV, and a third flexure 60, comparable tothe flexure 40 of Figure IV. The flexure set 56, 57 has a pair ofcooperating contacts 61, 62, and the flexure set 58, 59 has a pair ofcooperating contacts 63, 64. The ilexures 56 and 58 are joined at theirouter ends by a rigid cross bar 65 by means of rivets 66, and theflexure 60 is provided with an actuating pin 67, comparable to the pin47 of Figure IV, for engaging the cross bar 65 as a means ofsimultaneously opening or closing both contact pairs 61, 62 and 63, 64in the manner and by means of similar flexure bias and mountingarrangements, with respect to the showing in and the description hereinof Figure IV.

Again as shown in Figures IX and X, the flexure 68 has a magneticmaterial strip 68 mounted thereon, and various spacer, insulating andmounting plates are provided vertically between the fiexures, with thewhole assembly held together by screws 69. Electrical connection leads56', 57, 5 and 59 are provided respectively on the flexures 56-59. Theonly magnetic material within range of the rotary magnet as assembled isthe magnetic strip 68.

This invention, therefore, provides a new and useful rotary magnetmultiple switch, wherein compact and improved switch structure isprovided, and wherein an embodiment provides contacts immersed in oilwith resultant features of safety and long contact life.

As many embodiments may be made of the above invention, and as changesmay be made in the embodiments set for above, without departing from thescope of the invention, it is to be understood that all matterhereinbefore set forth or shown in the accompanying drawings is to beinterpreted as illustrative only and not in a limiting sense.

I claim:

For use in multi-measurement instruments wherein a series of differentvariable conditions are repeatedly measured by a single instrumentthrough the use of an automatic electrical switching unit with a highdegree of explosion proof character and which connects in serial mannera plurality of measurement elements to a common circuit in saidinstrument; a generally cylindrical, compact, essentially fullyenclosed, rotary magnetic switch unit wherein a series of electricaldouble switch assemblies in an oil bath in a single chamber are actuatedas a magnet is rotated within said unit, said unit comprising, incombination, a single, completely closed metallic chamber housing havingone end in cylindrical form and the other end in cylindrical annularform, with circumferentially spaced switch assembly mounting supportsextending through said one end cylinder form in apertured continuance ofthe inner wall of said cylindrical annular form, a body of electricallynon-conductive oil substantially filling said closed chamber, a seriesof electrical double switch assemblies, mounted in a circle around saidannular formation and within said chamber, with one of said switchassemblies mounted on each of said switch assembly mounting supports,each of said switch assemblies being elongated in form and extendinglengthwise of the whole switch unit and essentially through both thecylindrical form and the cylindrical annular form of said closed chamberin parallel with the longitudinal axis of the whole switch unit, each ofsaid double switch assemblies comprising a single flexure arm lyingadjacent the inner wall of said cylindrical annular form of said closedchamber, a magnetic material armature strip fixed to said single flexurearm and lying between said single flexure arm and the inner wall of saidcylindrical annular form of said closed chamber, a switch operating pinon an end of said single flexure arm which lies in said cylindricalannular form of said closed chamber, with said single flexure arm formedand mounted with self spring bias radially outward from the longitudinalaxis of the whole switch unit, a first pair of contact arms electricallyinsulatedly spaced side by side and radially outward with respect tosaid single flexure arm and the longitudinal axis of the whole switchunit, each of said first pair of contact arms having an electricalcontact button radially outwardly facing and located at an end of itsrespective contact arm which lies in said cylindrical annular form ofsaid closed chamber, with said first pair of contact arms of equallength and shorter than said single flexure arm, whereby said singleflexure arm switch operating pin extends radially outward past the saidfirst pair of contact arms, a second pair of flexible contact armselectrically insulatedly spaced side by side and radially outward withrespect to said first pair of contact arms, each of said second pair ofcontact arms having an electrical contact button for circuit closingengagement with a respective one of said first contact arm contactbuttons, said second pair of contact arms being essentially of equallength with each other and with said single flexure arm, with anelectrical insulation cross-piece joining said second pair of contactarms as an engagement member for said switch operating pin, said secondpair of contact arms being formed and mounted with self spring biasradially inward, said bias being normally overcome by the radiallyoutward bias of said single flexure arm, whereby said contact buttonsare all normally separated, the mounting of said arms comprising alamination of arms and separators in the cylindrical form of said closedchamber and on a respective one of said switch mounting supports, withsaid contact arms having electrical leads therefrom extendingindividually through the wall of said housing in insulated relationtherewith, a second, cylindrical chamber, defined by the cylindricalannular form of said closed chamber, and a magnet assembly with a largeportion thereof in said second chamber, said magnet assembly comprisinga base with spaced peripheral uprights supporting said closed chamberhousing, a fixed center post extending into said second chamber alongthe longitudinal axis of said whole switching unit, a mounting sleeverotatably mounted on said center post and having an annular abutmentthereon, and a magnet assembly comprising a driving gear on saidmounting sleeve against one side of said abutment, a first magnet polepiece on said mounting sleeve against the other side of said abutment, amagnet in the form of a spacer sleeve on said mounting sleeve and withone end against said first pole piece, a second magnet pole piece onsaid mounting sleeve and against the other end of said magnet, and apair of bolts extending through said driving gear and said pole piecesto hold said magnet assembly together, said pole pieces being mountedtransversely of and ofif center on said mounting sleeve to formextensions of said magnet which extend to adjacency with saidcylindrical annular form of said closed chamber and to said magneticarmature strips therein in turn as said magnet is rotated by theoperation of said gear.

References Cited in the file of this patent UNITED STATES PATENTS922,673 Crist May 25, 1909 980,863 Burnham Jan. 3, 1911 1,530,936Greenwood Mar. 24, 1925 2,310,138 Whittaker Feb. 2, 1943 FOREIGN PATENTS277,787 Great Britain Sept. 29, 1927 720,957 France Dec. 12, 1931

